The present invention relates generally to control systems for internal combustion engines, and more particularly, to an electronic throttle position feedforward system.
Many previously known motor vehicle throttle controls have a direct physical linkage between an accelerator pedal and the throttle so that the throttle plate is pulled open by the accelerator cable as the driver presses the pedal. The direct mechanical linkage includes a biasing force that defaults the linkage to a reduced operating position, also known as idle, in a manner consistent with regulations. Nevertheless, such mechanisms are often simple and unable to adapt fuel efficiency or minimizing regulated emissions or enhancing driveability to changing traveling conditions, and add significant weight and components to the motor vehicle.
An alternative control for improving throttle control and the precise introduction of fuel air mixtures into the engine cylinders is provided by electronic throttle controls. The electronic throttle control includes a throttle control unit that positions the throttle plate by an actuator controlled by a microprocessor based on sensor input. The processors are often included as part of a powertrain electronic control that can adjust the fuel and air intake and ignition in response to changing conditions of vehicle operation as well as operator control. Protection may be provided so that an electronic system does not misread or misdirect the control and so that unintended operation is avoided when portions of the electronic control suffer a failure.
The throttle control unit that positions the throttle plate must accelerate and decelerate a mass with torque such that a given position is attained. U.S. Pat. No. 4,947,815 discloses a positioning device for a throttle flap of an internal combustion engine wherein the positioning element is electrically adjusted via a positioning motor on the basis of the driver command derived from a pedal actuation of the driver and other inputs. When the position control is acting against a known biasing torque of force, that force may be compensated for with a feedforward term. In this way, the integral control does less work and positioning performance is improved. U.S. Pat. No. 5,809,966 applies this concept to a controller for a motorized throttle. The invention described in the xe2x80x2966 patent bases its feedforward term on actual position. Unfortunately, this results in sub-optimal performance.
The disadvantages associated with these conventional throttle plate positioning techniques have made it apparent that a new technique using a feedforward term for throttle plate positioning is needed. The new technique should provide unproved performance over a feedforward system based on a driver-commanded throttle plate position. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable electronic throttle position feedforward system. Another object of the invention is to improve performance over a feedforward system based on actual throttle plate position.
In accordance with the objects of this invention, an electronic throttle position feedforward system is provided. In one embodiment of the invention, a method for controlling a positioning device of an internal combustion engine includes the steps of: providing an electric motor for actuating the throttle by applying a torque to the motor which changes sign over the positioning range; generating a drive signal for the motor in the context of a position control based upon a commanded position, whereby the drive signal controls the voltage applied to the motor and thus the current through the motor; and, changing the drive signal to abruptly change the applied motor voltage when commanded position is in the region of the torque reversal.
The present invention thus achieves an improved electronic throttle position feedforward system. The present invention is advantageous in that the performance is improved over a feedforward system based on actual throttle plate position by basing throttle plate position on commanded position.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.